Runa Tokisaka originates as Kyosuke Date's fraternal twin sister in "The SoulTaker." Chronologically seventeen, she usually manifests as a five-year-old child due to the separation of her spirit fragments, called Flickers. Reuniting all Flickers restores her true seventeen-year-old form, allowing her transformation into the mutant SoulAnubis. Manipulated by the Kirihara Corporation and her father, Dr. Richard Vincent, who aims to exploit her ability to generate Beta Applicon viruses, she serves as the primary antagonist. Her backstory reveals her mother, Tsubaki Tokisaka, stabbed her during their escape from pursuers to awaken her latent mutant powers. These Flickers represent splintered aspects of her psyche, including one modeled after Tsubaki. Her arc concludes by confronting Kyosuke and the Kirihara Corporation, resulting in the permanent dispersion of her Flickers.

In the parody spinoff "Nurse Witch Komugi," Runa is reimagined as a child star working at the Kiri Pro talent agency alongside Komugi Nakahara. She retains her young childlike appearance. Her personality shifts dramatically to that of a manipulative and cynical diva. She strategically leverages her cute exterior for professional gain, exploiting others' perceptions to secure advantages or roles. Despite her innocent facade, she harbors intense, unexplained hostility towards Komugi, frequently insulting her flat chest and deriding her as a "pseudo-idol." This animosity manifests privately, such as through punching a sandbag adorned with Komugi's image. Kyosuke is recast as a fellow idol and Komugi's romantic interest, with no acknowledgment of their original familial connection. Within this parody, Runa functions as a static comedic rival, devoid of supernatural elements or character development.